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A safety margin must always be maintained between trains. To this end, position data of all trains must be provided to the railway system in real time. Basically, this data has been provided based on the infrastructure installed on the railway. However, enormous costs are required to install the infrastructure, and continuous maintenance is required. In addition, cases of accidents due to un-detection or false-detection of trains are being reported as news. Due to these problems, researches on infra-less navigation system for trains have been conducted. Taking into account the blocking phenomenon of Global Positioning System (GPS)/Global Navigation Satellite System (GNSS) signals in tunnels, the navigation system for trains should constitute an integrated navigation system. However, the accuracy and reliability of navigation solution provided by the integrated navigation system are not always satisfied. And this can lead to instability of the railway system. Therefore, the navigation solution for trains must have high accuracy and also the reliability information of the corresponding navigation solution must be provided. In this article, we construct an Inertial Navigation System (INS)/GPS/Non-Holonomic Constraints (NHC) integrated navigation system for trains with NHC motion. A simulation trajectory is generated considering the real trajectory, and the accuracy and reliability of the navigation information according to the trajectory and measurements are analyzed together. And based on this information, we propose a method to calculate the safety margin between trains. The performance of the proposed technology is verified through a real trajectory-based Monte Carlo simulation.

We illuminate how the tunnel magnetoresistance (TMR) of MgO-based magnetic tunnel junctions (MTJs) is affected by the structure, materials, and fabrication processes. First, we demonstrate a possibility to control detrimental diffusions by separating a step for obtaining a grain-to-grain epitaxy in CoFeB/MgO/CoFeB layers from a step for achieving a high exchange-bias field in the pinned layer. A high TMR and large exchange-bias field can be obtained simultaneously by circumventing Mn diffusion and minimizing Ru diffusion during the annealing process at high temperature. Second, we show that the MTJs consisting of CoFeB/ MgO/ CoFeB/ Ru/ ferromagnet (FM), where FM is Co, Ni, NiFe, CoFe, or CoFeB, can provide a reasonably high TMR and decent thermal stability, presumably useful for the memory applications.

Railway signaling system is the core technology to secure safety and punctuality. The system in Korea is currently applied to each railway organization with a differently and independently developed form handed from various signaling systems of other countries. The problem from the above reason makes the identification time of the causes of failure and the maintenance time longer, makes the quality of the railway operation, the service quality for the general public degraded, makes relevant matters to its interoperability, operation, maintenance, and training difficult even for the same functions, and thus, results in excessively expensive expenses. To make a preparation for the continuous expansion of the urban transit lines, and the improvement of the existing urban transit ones, the advanced standardization of signaling systems, which is following the current technological trend, is required. As the demands of the improvement of our own technologies and the security of compatibility among different products, studies on establishing standard specifications and safety standards are conducted. In this paper the structure of the standard specification and the safety criterion are represented.

This paper presents a control system design for personal rapid transit (PRT) system and a configuration of apparatus to assess its control scheme. The control system can be divided into two parts: one is for the vehicle management that is related with the supervision of the vehicle operation and the other is for the vehicle operational control that is placed in the lower position of the control hierarchy. In this paper we focus on the vehicle operational control scheme that is one of the important features of PRT to guarantee PRT system performance. The operational control scheme that can be implemented by using the commercial process boards is proposed and a simple vehicle control algorithm for test is uploaded to it. The calculation results of the process boards are compared with the simulation results that are produced from a combined platform of Matlab/Simulink and Labview Simulation Interface Toolkit.

Experimental results on the current induced magnetization switching of nano-patterned IrMn/CoFe/Cu/CoFe spin-valves are reported. The main emphasis is the increase of MR and the reduction of the critical current density through an improved fabrication process. A method using a batch-fabricated trilayer template is developed with the junction features defined by a platinum(Pt) stencil mask. Nano-pillars with the lateral dimensions (150times80 nm2) are fabricated by electron-beam lithography, including a wet etching to form a nanotemplate. A key to the improved fabrication process is the formation of the recessed part of the SiO2 layer which helps to reduce the shadow effect during the deposition of the spin valve multilayers into the nanotemplate. Both the MR ratio and the critical current density are enhanced by the new improved fabrication process. The observed critical current density is 5.98times106 A/cm2, which is significantly smaller than the value of 1.16times108 A/cm2 observed in a similar device fabricated using a conventional fabrication process.

We have studied the current induced magnetization switching (CIMS) in cobalt-based spin valve structures. Two exchange bias spin valves with extended fixed ferromagnets adopted as a current lead have been chosen for the study. The difference between them is that in the first structure, labeled EBSV (Exchange-Biased Spin Valve), no nano-oxide layer (NOL) was applied, while in the second structure, named NOL-EBSV, a NOL is inserted into the exchange biased pinned ferromagnet lead. The CIMSs in these two structures and in a non-exchange biased one, called SSV serving as the reference sample, have been studied. The temperature and field dependence of switching current in EBSV and SSV are also investigated for a better understanding the effect of exchange pinning field on the CIMS. The experiment result of CIMS in the EBSV shows a significant reduction in switching current density by a factor of 4.8, compared with a non-exchange biased spin valve with similar layer thicknesses. A double large reduction of switching current density is observed in the NOL-EBSV. We qualitatively analyze the effect of the exchange bias pinning field as well as of the nano-oxide layer on the reduction of switching current. A quantitative interpretation of the enhancement of CIMS by nano- oxide layer has been done by a three dimensional calculation of spin transport in EBSV and NOL-EBSV.

Spin transfer from polarized conduction electrons to the free layer’s magnetic moment is considerably enhanced when the fixed layer of a spin valve is magnetically pinned by an exchange bias antiferromagnet. This enhancement leads to significantly lower threshold current densities for spin transfer magnetization switching and to much higher total current induced effective fields. The phase diagram is not symmetric as in non-exchange biased spin valves but asymmetric over the field axis.

We have observed the negative value of longitudinal resistance in a InAs two-dimensional electron gas (2DEG) system in which magnetic barriers have been made in the form of the serial junctions of positive and negative magnetic-field regions. When the transport mechanism is ballistic (at low temperature), the measured longitudinal resistance of our device shows negative or positive values depending on the sign of the externally applied magnetic field.

We studied spin transfer torque in nanofabricated pillars with |CoFe/Pd]2 double free-layers. This sample showed various spin transfer switching properties as a function of external magnetic fields. We report the first observation of two-step switching and the inversion of f Ic APrarrP and Ic APrarrP characterized by spin directions of three magnetic layers. Telegraph noise confirms the inversion in single domain model.

Multilayered Co/Pd nanowire array were obtained from atomic image projection electron beam lithography (AIPEL) and combined novel etching technique using amorphous Si layer. The role of dipolar interaction in magnetic anisotropy of the nanowire array was studied. The structural information were obtained by HR-TEM, XRD, SEM and AFM. The magnetic properties were measured by SQUID and vibrating sample magnetometry.

Two kinds of Co thin film nanomagnets with multi-domain and single-domain in the structure of IrMn (8 nm)/Co (11 nm)/Cu (2 nm)/Co (2 nm)/Cu (2 nm)/Au (5 nm)/Cu (100 nm) are prepared and the resistance change by the magnetic field and electric current have been studied. From current induced magnetization switching (CIMS) and pulse effect, it is estimated that the switching time in the multi-domain CIMS device is smaller than 2 nsec and would suggest that the domain structure is a crucial factor in determining the switching time, not the switching current.

In this research, the angle dependance of Hall voltage and pulse-induced magnetization switching (PIMS) have been studied by electrical transport measurements in the Hall-bar shaped (Ga,Mn)As. Planar Hall data might be governed by a magnetization switching at low field and also the switching could be easily induced by voltage pulses. When the amplitude of the pulse is higher, the switching is more quickly achieved.

The spin susceptibility of HgCdTe 2DEG system was measured in this study with two independent methods which yielded the same value. It is remarkably large compared to any other 2DEG system. The large value of spin susceptibility as well as the large g-factor are the unique properties of HgCdTe which can be utilized as spintronic material.

The magnetization reversal of a lateral submicrometer-sized magnetic layer by a spin-polarized current has been known recently. In this work, the current induced magnetization switching effect at RT in an exchange biased spin valve with nano oxide layer structure is reported for the first time. A great enhancement of the effect has been observed. The critical switching current can be lowered by about one order compared to that in a simple trilayer spin valve with similar layer thickness. The product of the absolute resistance change and the junction area is almost three times larger than that in the simple spin valve.

SiO/sub 2//Ta(50 /spl Aring/)/Ni/sub 81/Fe/sub 19/(60 /spl Aring/)/Fe/sub 50/Mn/sub 50/(80 /spl Aring/)/FM/sub BOTTOM/(40 /spl Aring/)/Al/sub 2/O/sub 3/(12-16 /spl Aring/)/FM/sub TOP/(100 /spl Aring/)/Ta(20 /spl Aring/) are prepared on a thermally oxidized Si(100) substrate. FM layer used is Ni/sub 81/Fe/sub 19/ or Co/sub 84/Fe/sub 16/. The effect of substrate-biased plasma etching process on magnetotransport properties in magnetic tunnel junctions compared to that of the device prepared by a conventional way is investigated. Several properties such as TMR ratio and junction resistance, magnetization switching behavior of the MTJs are also investigated.

Dielectric/Metal/Dielectric (D/M/D) multi films can find the electronic and optical application as components of advanced materials design. We investigated the diffraction efficiency of holography using amorphous MgF/sub 2//Ag/As/sub 40/Ge/sub 10/Se/sub 15/S/sub 35/ multi-layer thin films. Multi-layer structures were formed by alternating a layer of dielectric(MgF/sub 2/) metal(Ag) and chalcogenide (As/sub 40/Ge/sub 10/Se/sub 15/S/sub 35/) in order to be increase the diffraction efficiency. The holographic grating recording in these thin films has been formed using He-Ne laser light (632.8 nm) under the intensity and the phase polarization holography) The diffraction efficiency was obtained by +1st order intensity. As the results, we found the high diffraction efficiency on multi-layer films. The maximum diffraction efficiency of intensity and phase polarization holography was 24% and 15%.

In this paper, we present the magnetotransport properties of the electroplated and sputtered Bi thin film in the temperature range 4-300 K.

Summary form only given. The AlOx tunnel barrier is a critical and sensitive layer in magnetic tunnel junctions (MTJ). The natural oxidation and the plasma oxidation methods are generally employed to fabricate this layer. In this study, the microstructures and properties of the AlOx layer formed by both methods were compared.